typedef struct ThreadSpecificData {
    int asyncReady;		/* This is set to 1 whenever a handler becomes
				 * ready and it is cleared to zero whenever
				 * Tcl_AsyncInvoke is called. It can be
				 * checked elsewhere in the application by
				 * calling Tcl_AsyncReady to see if
				 * Tcl_AsyncInvoke should be invoked. */
    bool asyncActive;		/* Indicates whether Tcl_AsyncInvoke is
				 * currently working. If so then we won't set
				 * asyncReady again until Tcl_AsyncInvoke
				 * returns. */
} ThreadSpecificData;
static Tcl_ThreadDataKey dataKey;

/* Mutex to protect linked-list of AsyncHandlers in the process. */

    Tcl_MutexLock(&asyncMutex);

    if (tsdPtr->asyncReady == 0) {
	Tcl_MutexUnlock(&asyncMutex);
	return code;
    }
    tsdPtr->asyncReady = 0;
    tsdPtr->asyncActive = true;
    if (interp == NULL) {
	code = TCL_OK;
    }

    /*
     * Make one or more passes over the list of handlers, invoking at most one
     * handler in each pass. After invoking a handler, go back to the start of
     * the list again so that (a) if a new higher-priority handler gets marked
     * while executing a lower priority handler, we execute the higher-

	    break;
	}
	asyncPtr->ready = 0;
	Tcl_MutexUnlock(&asyncMutex);
	code = asyncPtr->proc(asyncPtr->clientData, interp, code);
	Tcl_MutexLock(&asyncMutex);
    }
    tsdPtr->asyncActive = false;
    Tcl_MutexUnlock(&asyncMutex);
    return code;
}

/*
 *----------------------------------------------------------------------
 *